Various types of filters are known for filtering water and similar liquids. A particularly useful type of filter is a disk filter. Filters of this type are described and claimed, for example, in applicant's U.S. patent applications Ser. Nos. 647,094 which is now U.S. Pat. No. 4,624,785, filed Sept, 4, 1984; 709,371, filed Mar. 7, 1985 which is now; abandoned 709,372, filed Mar. 7, 1985 which is now U.S. Pat. No. 4,683,060; 709,373, filed Mar. 7, 1985 which is now U.S. Pat. No. 4,654,143; and U.S. Pat. Nos. 4,026,806; 4,042,504; 4,045,345; 4,271,018; 4,278,540; 4,295,963.